Not only do people who walk to the shops spend more but overall, the nicer the environment, the more people spend.

A recent study in Aberdeen of Union Street Pedestrianisation (a current project) found projections of
"direct benefits of 410 new FTE (full time equivalent) jobs (mainly retail and hospitality) and £22m increased turnover to City Centre businesses.

The City of Toronto report Economic Benefits of Pedestrianisation Toronto 1999 found "Pedestrian-orientated retail streets can provide significant environmental improvements and increases local retail sales".

There is a theory that car traffic is good for retail. However, in Leicester, UK, the greater the level of car traffic, the greater the number of vacant shops (Newby et al. 1992).

Pedestrian traffic tends to increase dramatically after a pedestrian friendly area is created (TEST 1989). Shoppers are drawn by the pleasant shopping experience, safety, improved air quality and low noise levels (Newby, et al. 1991, Forest 1981).
Greater pedestrian traffic usually leads to increased sales. World-wide, far more pedestrianisation schemes have had a positive effect on retail turnover (49%) than a negative on (2%); other projects have had a neutral effect (TEST 1989).

The town of Hasselt (Belgium) made its streets friendly to pedestrians and introduced free transit for residents. This improved business, thereby increasing municipal revenue and allowing the city to reduce it business taxation rates (CNN 1998).
Pedestrianisation and reduction of car traffic improves shop occupation rates and rents.

In France, shop occupancy increases after pedestrianisation, as do property values and shop rents, because of increased competition for storefronts (Forest 1982). This can be followed by the displacement of weaker businesses by stronger ones, notably chain stores and luxury goods stores (Forest 1982).
Office rental rates benefit from pedestrian friendly surroundings.

In Dallas, Texas, office buildings with landscaping and good pedestrian amenities tend to have higher occupancy rates than others (Goldsteen 1989).

In Toronto, the underground PATH network is very popular among local workers. Buildings connected to the PATH charge twice the annual rent per square foot and have lower vacancy rates than comparable buildings that are not on the PATH (Campbell 1999).
Around the world, cities where people mostly walk, cycle or use public transit, have greater wealth (gross regional product per capita) than cities with heavy car use (Newman 1998).
-Newman (1998) attributes the negative impact of heavy car use on city wealth to: (1) greater road expenditure, (2) greater percentage of wealth spent on commuting, (3) reduced transit cost recovery, (4) increased transportation deaths, and (5) increased pollution from vehicle emissions
See http://www.toronto.ca/legdocs/1999/agendas/council/cc/cc990413/ed6rpt/cl001.htm